Calculating the Final Temp of an XK8 Cylinder Using the Ideal Gas Law

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Homework Help Overview

The discussion revolves around calculating the final temperature of air in a Jaguar XK8 engine cylinder using the ideal gas law. The problem involves initial and final conditions of pressure and volume during the compression stroke of the engine.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • The original poster attempts to apply the ideal gas law by using the relationship between pressure, volume, and temperature. Some participants question the necessity of volume conversion and emphasize the importance of using Kelvin for temperature calculations.

Discussion Status

Participants are actively discussing the correct approach to the problem, with some offering guidance on temperature conversion and the use of ratios. There is no explicit consensus yet, but the conversation is focused on clarifying assumptions and correcting initial mistakes.

Contextual Notes

There is mention of a potential oversight regarding temperature units and the need for absolute pressure calculations. The original poster's calculations may be affected by these factors.

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A Jaguar XK8 convertible has an eight-cylinder engine. At the beginning of its compression stroke, one of the cylinders contains 499cm^3 of air at atmospheric pressure (1.01×105 Pa and a temperature of 27.0 C. At the end of the stroke, the air has been compressed to a volume of 46.2 cm^3 and the gauge pressure has increased to 2.72×106 Pa. Compute the final temperature.

I ended up with 69.8 degrees. I used the ideal gas law, but because the mass of air remains constant, i used:

(p1v1/T1) = (p2v2/T2)

I converted the volume to 4.99 x 10^-4 and 4.62 x 10^-5. I also dtermined the final absolute pressure, which is 2.821 x 10^6. But my answer is wrong. Could someone please help.
 
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It's ok...i forgot to convert to Kelvin.
 
Classical mistake.The weird part is that u converted the volume...:eek:

Daniel.
 
Use the ratios of the volumes, so as dex said you don't need to convert. Also, as you understood, always work with Kelvin!
 
I hope u see that u need the conversion to K in both the initial & final temperature...

Daniel.
 
How did you find the final absolute pressure?
 

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